Many methods and processes are known to clean, purify, clarify and otherwise treat fluids for proper disposal, consumption, use, and other needs. These methods include, but are not necessarily limited to, centrifugation and filtration to remove particulates, chemical treatments to sterilize water, distillation to purify liquids, decanting to separate two phases of fluids, reverse osmosis to desalinate liquids, electrodialysis to desalinate liquids, pasteurization to sterilize foodstuffs, and catalytic processes to convert undesirable reactants into useful products. Each of these methods is well-suited for particular applications and typically a combination of methods is used for a final product.
There are many different known technologies available for the sterilization of liquids. Adsorption, chemical treatments, ozone disinfection, and ultraviolet (UV) irradiation all perform very well for the removal of pathogenic microbes. However, each of these technologies has limitations, including overall efficacy, initial capital cost, operating cost, byproduct risk, necessary pre-treatment of liquid, hazardous compounds used or produced, and which thus must be properly disposed of, and other limitations.
Although chemical methods are the most widespread in use, they have a number of shortcomings. Such drawbacks include increasing microbiological adaptation to their destructive effects, safety hazards associated with chlorine use and storage, and environmental impact. UV is a popular treatment, but the liquid must be clear in order for it to be effective, and it does not break down any biofilm formation; it is also very expensive to install and operate. In industrial and municipal applications such as water and wastewater plants, the three most widely used methods of liquid sterilization are ozone treatment, chlorine treatment, and UV irradiation.
Desalination of liquids is highly useful for drinking water, biological fluids, medicines, chemicals, petroleum and its derivatives, and many other liquids. In addition, desalination of water would be beneficial since less than 0.5% of the Earth's water is directly suitable for human consumption, agricultural, or industrial uses. Consequently, desalination is finding increasing favor to produce potable water from brackish groundwater and seawater since it makes the other approximately 99.5% of the water available. There are five basic desalination methods: thermal, reverse osmosis, electrodialysis, ion exchange, and freezing. Thermal and freezing processes remove fresh water from saline leaving behind concentrated brine. Reverse osmosis and electrodialysis employ membranes to separate salts from fresh water. Ion exchange involves passing salt water over resins which exchange more desirable ions for less desirable dissolved ions. Only thermal and reverse osmosis processes are currently commercially viable. Even so, these two methods tend to be prohibitive due to their expense.
Further, fluids produced from subterranean formations, such as underground reservoirs, including but not necessarily limited to hydrocarbons such as crude oil and gas, and associatively produced water, may contain dangerous or undesirable contaminants and particulates. Produced water from the shale gas plays in North America is becoming especially problematic. Such contaminants may include, but are not necessarily limited to, heavy metals, heavy metal compounds, heavy metal complexes, radioactive metals, radioactive compounds, radioactive complexes and combinations thereof. These radioactive materials include, but are not necessarily limited to naturally occurring radioactive materials (NORM) such as uranium, thorium, potassium, radium, radon, lead and barium or strontium scales.
Heavy metals are defined herein to include, but are not necessarily limited to, mercury, arsenic, cadmium, uranium, plutonium, lead, vanadium, tungsten, iron, cobalt, copper, manganese, molybdenum, zinc, selenium, and combinations thereof. An alternative definition according to N. I. Sax, et al., Hawley's Condensed Chemical Dictionary, Eleventh Edition, Van Nostrand Reinhold, New York, 1987, p. 588 is a “metal of atomic weight greater than sodium (22.9) that forms soaps on reaction with fatty acids, e.g. aluminum, lead, cobalt.” It will be understood that the heavy metals are generally present as ions, and thus removing heavy metals from water means removing heavy metal ions. In our lab tests, both arsenic and mercury are ions. Certain of these metals are well known to be dangerous and undesirable due to toxicity concerns including, but not necessarily limited to, mercury, arsenic, cadmium, uranium, and lead. Some of these materials may pose a health, safety and/or environmental (HS&E) risk, and thus exposure of these materials to humans and/or the environment should be minimized or avoided completely.
There is always a need to develop new structures and methods that will help perform these filtration and removal processes more cost effectively than their traditional counterparts. In the area of liquid filtration and purification, any technology that can lower the overall cost, simplify the process, increase safety and improve efficiencies would be very advantageous. It would thus be desirable if methods and/or structures would be devised to filter and purify liquids, such as wastewater and fluids produced during hydrocarbon recovery, using simple methods and devices.